package server

import (
	"context"
	"fmt"
	"net/netip"
	"unicode/utf8"

	"github.com/rs/xid"

	"github.com/netbirdio/netbird/management/domain"
	"github.com/netbirdio/netbird/management/proto"
	"github.com/netbirdio/netbird/management/server/activity"
	"github.com/netbirdio/netbird/management/server/status"
	"github.com/netbirdio/netbird/route"
)

// GetRoute gets a route object from account and route IDs
func (am *DefaultAccountManager) GetRoute(ctx context.Context, accountID string, routeID route.ID, userID string) (*route.Route, error) {
	unlock := am.Store.AcquireAccountWriteLock(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return nil, err
	}

	user, err := account.FindUser(userID)
	if err != nil {
		return nil, err
	}

	if !(user.HasAdminPower() || user.IsServiceUser) {
		return nil, status.Errorf(status.PermissionDenied, "only users with admin power can view Network Routes")
	}

	wantedRoute, found := account.Routes[routeID]
	if found {
		return wantedRoute, nil
	}

	return nil, status.Errorf(status.NotFound, "route with ID %s not found", routeID)
}

// checkRoutePrefixOrDomainsExistForPeers checks if a route with a given prefix exists for a single peer or multiple peer groups.
func (am *DefaultAccountManager) checkRoutePrefixOrDomainsExistForPeers(account *Account, peerID string, routeID route.ID, peerGroupIDs []string, prefix netip.Prefix, domains domain.List) error {
	// routes can have both peer and peer_groups
	routesWithPrefix := account.GetRoutesByPrefixOrDomains(prefix, domains)

	// lets remember all the peers and the peer groups from routesWithPrefix
	seenPeers := make(map[string]bool)
	seenPeerGroups := make(map[string]bool)

	for _, prefixRoute := range routesWithPrefix {
		// we skip route(s) with the same network ID as we want to allow updating of the existing route
		// when creating a new route routeID is newly generated so nothing will be skipped
		if routeID == prefixRoute.ID {
			continue
		}

		if prefixRoute.Peer != "" {
			seenPeers[string(prefixRoute.ID)] = true
		}
		for _, groupID := range prefixRoute.PeerGroups {
			seenPeerGroups[groupID] = true

			group := account.GetGroup(groupID)
			if group == nil {
				return status.Errorf(
					status.InvalidArgument, "failed to add route with %s - peer group %s doesn't exist",
					getRouteDescriptor(prefix, domains), groupID,
				)
			}

			for _, pID := range group.Peers {
				seenPeers[pID] = true
			}
		}
	}

	if peerID != "" {
		// check that peerID exists and is not in any route as single peer or part of the group
		peer := account.GetPeer(peerID)
		if peer == nil {
			return status.Errorf(status.InvalidArgument, "peer with ID %s not found", peerID)
		}
		if _, ok := seenPeers[peerID]; ok {
			return status.Errorf(status.AlreadyExists,
				"failed to add route with %s - peer %s already has this route", getRouteDescriptor(prefix, domains), peerID)
		}
	}

	// check that peerGroupIDs are not in any route peerGroups list
	for _, groupID := range peerGroupIDs {
		group := account.GetGroup(groupID) // we validated the group existence before entering this function, no need to check again.

		if _, ok := seenPeerGroups[groupID]; ok {
			return status.Errorf(
				status.AlreadyExists, "failed to add route with %s - peer group %s already has this route",
				getRouteDescriptor(prefix, domains), group.Name)
		}

		// check that the peers from peerGroupIDs groups are not the same peers we saw in routesWithPrefix
		for _, id := range group.Peers {
			if _, ok := seenPeers[id]; ok {
				peer := account.GetPeer(id)
				if peer == nil {
					return status.Errorf(status.InvalidArgument, "peer with ID %s not found", peerID)
				}
				return status.Errorf(status.AlreadyExists,
					"failed to add route with %s - peer %s from the group %s already has this route",
					getRouteDescriptor(prefix, domains), peer.Name, group.Name)
			}
		}
	}

	return nil
}

func getRouteDescriptor(prefix netip.Prefix, domains domain.List) string {
	if len(domains) > 0 {
		return fmt.Sprintf("domains [%s]", domains.SafeString())
	}
	return fmt.Sprintf("prefix %s", prefix.String())
}

// CreateRoute creates and saves a new route
func (am *DefaultAccountManager) CreateRoute(ctx context.Context, accountID string, prefix netip.Prefix, networkType route.NetworkType, domains domain.List, peerID string, peerGroupIDs []string, description string, netID route.NetID, masquerade bool, metric int, groups []string, enabled bool, userID string, keepRoute bool) (*route.Route, error) {
	unlock := am.Store.AcquireAccountWriteLock(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return nil, err
	}

	if len(domains) > 0 && prefix.IsValid() {
		return nil, status.Errorf(status.InvalidArgument, "domains and network should not be provided at the same time")
	}

	if len(domains) == 0 && !prefix.IsValid() {
		return nil, status.Errorf(status.InvalidArgument, "invalid Prefix")
	}

	if len(domains) > 0 {
		prefix = getPlaceholderIP()
	}

	if peerID != "" && len(peerGroupIDs) != 0 {
		return nil, status.Errorf(
			status.InvalidArgument,
			"peer with ID %s and peers group %s should not be provided at the same time",
			peerID, peerGroupIDs)
	}

	var newRoute route.Route
	newRoute.ID = route.ID(xid.New().String())

	if len(peerGroupIDs) > 0 {
		err = validateGroups(peerGroupIDs, account.Groups)
		if err != nil {
			return nil, err
		}
	}

	err = am.checkRoutePrefixOrDomainsExistForPeers(account, peerID, newRoute.ID, peerGroupIDs, prefix, domains)
	if err != nil {
		return nil, err
	}

	if metric < route.MinMetric || metric > route.MaxMetric {
		return nil, status.Errorf(status.InvalidArgument, "metric should be between %d and %d", route.MinMetric, route.MaxMetric)
	}

	if utf8.RuneCountInString(string(netID)) > route.MaxNetIDChar || netID == "" {
		return nil, status.Errorf(status.InvalidArgument, "identifier should be between 1 and %d", route.MaxNetIDChar)
	}

	err = validateGroups(groups, account.Groups)
	if err != nil {
		return nil, err
	}

	newRoute.Peer = peerID
	newRoute.PeerGroups = peerGroupIDs
	newRoute.Network = prefix
	newRoute.Domains = domains
	newRoute.NetworkType = networkType
	newRoute.Description = description
	newRoute.NetID = netID
	newRoute.Masquerade = masquerade
	newRoute.Metric = metric
	newRoute.Enabled = enabled
	newRoute.Groups = groups
	newRoute.KeepRoute = keepRoute

	if account.Routes == nil {
		account.Routes = make(map[route.ID]*route.Route)
	}

	account.Routes[newRoute.ID] = &newRoute

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return nil, err
	}

	if isRouteChangeAffectPeers(&newRoute) {
		am.updateAccountPeers(ctx, account)
	}

	am.StoreEvent(ctx, userID, string(newRoute.ID), accountID, activity.RouteCreated, newRoute.EventMeta())

	return &newRoute, nil
}

// SaveRoute saves route
func (am *DefaultAccountManager) SaveRoute(ctx context.Context, accountID, userID string, routeToSave *route.Route) error {
	unlock := am.Store.AcquireAccountWriteLock(ctx, accountID)
	defer unlock()

	if routeToSave == nil {
		return status.Errorf(status.InvalidArgument, "route provided is nil")
	}

	if routeToSave.Metric < route.MinMetric || routeToSave.Metric > route.MaxMetric {
		return status.Errorf(status.InvalidArgument, "metric should be between %d and %d", route.MinMetric, route.MaxMetric)
	}

	if utf8.RuneCountInString(string(routeToSave.NetID)) > route.MaxNetIDChar || routeToSave.NetID == "" {
		return status.Errorf(status.InvalidArgument, "identifier should be between 1 and %d", route.MaxNetIDChar)
	}

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return err
	}

	if len(routeToSave.Domains) > 0 && routeToSave.Network.IsValid() {
		return status.Errorf(status.InvalidArgument, "domains and network should not be provided at the same time")
	}

	if len(routeToSave.Domains) == 0 && !routeToSave.Network.IsValid() {
		return status.Errorf(status.InvalidArgument, "invalid Prefix")
	}

	if len(routeToSave.Domains) > 0 {
		routeToSave.Network = getPlaceholderIP()
	}

	if routeToSave.Peer != "" && len(routeToSave.PeerGroups) != 0 {
		return status.Errorf(status.InvalidArgument, "peer with ID and peer groups should not be provided at the same time")
	}

	if len(routeToSave.PeerGroups) > 0 {
		err = validateGroups(routeToSave.PeerGroups, account.Groups)
		if err != nil {
			return err
		}
	}

	err = am.checkRoutePrefixOrDomainsExistForPeers(account, routeToSave.Peer, routeToSave.ID, routeToSave.Copy().PeerGroups, routeToSave.Network, routeToSave.Domains)
	if err != nil {
		return err
	}

	err = validateGroups(routeToSave.Groups, account.Groups)
	if err != nil {
		return err
	}

	oldRoute := account.Routes[routeToSave.ID]
	account.Routes[routeToSave.ID] = routeToSave

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return err
	}

	if isRouteChangeAffectPeers(oldRoute) || isRouteChangeAffectPeers(routeToSave) {
		am.updateAccountPeers(ctx, account)
	}

	am.StoreEvent(ctx, userID, string(routeToSave.ID), accountID, activity.RouteUpdated, routeToSave.EventMeta())

	return nil
}

// DeleteRoute deletes route with routeID
func (am *DefaultAccountManager) DeleteRoute(ctx context.Context, accountID string, routeID route.ID, userID string) error {
	unlock := am.Store.AcquireAccountWriteLock(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return err
	}

	routy := account.Routes[routeID]
	if routy == nil {
		return status.Errorf(status.NotFound, "route with ID %s doesn't exist", routeID)
	}
	delete(account.Routes, routeID)

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return err
	}

	if isRouteChangeAffectPeers(routy) {
		am.updateAccountPeers(ctx, account)
	}

	am.StoreEvent(ctx, userID, string(routy.ID), accountID, activity.RouteRemoved, routy.EventMeta())

	return nil
}

// ListRoutes returns a list of routes from account
func (am *DefaultAccountManager) ListRoutes(ctx context.Context, accountID, userID string) ([]*route.Route, error) {
	unlock := am.Store.AcquireAccountWriteLock(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return nil, err
	}

	user, err := account.FindUser(userID)
	if err != nil {
		return nil, err
	}

	if !(user.HasAdminPower() || user.IsServiceUser) {
		return nil, status.Errorf(status.PermissionDenied, "only users with admin power can view Network Routes")
	}

	routes := make([]*route.Route, 0, len(account.Routes))
	for _, item := range account.Routes {
		routes = append(routes, item)
	}

	return routes, nil
}

func toProtocolRoute(route *route.Route) *proto.Route {
	return &proto.Route{
		ID:          string(route.ID),
		NetID:       string(route.NetID),
		Network:     route.Network.String(),
		Domains:     route.Domains.ToPunycodeList(),
		NetworkType: int64(route.NetworkType),
		Peer:        route.Peer,
		Metric:      int64(route.Metric),
		Masquerade:  route.Masquerade,
		KeepRoute:   route.KeepRoute,
	}
}

func toProtocolRoutes(routes []*route.Route) []*proto.Route {
	protoRoutes := make([]*proto.Route, 0)
	for _, r := range routes {
		protoRoutes = append(protoRoutes, toProtocolRoute(r))
	}
	return protoRoutes
}

// getPlaceholderIP returns a placeholder IP address for the route if domains are used
func getPlaceholderIP() netip.Prefix {
	// Using an IP from the documentation range to minimize impact in case older clients try to set a route
	return netip.PrefixFrom(netip.AddrFrom4([4]byte{192, 0, 2, 0}), 32)
}

// isRouteChangeAffectPeers checks if the given route affects any peers.
// A route affects peers if it has distribution groups, peer groups, or a routing peer.
func isRouteChangeAffectPeers(route *route.Route) bool {
	return len(route.Groups) != 0 || len(route.PeerGroups) != 0 || route.Peer != ""
}